Campbell, a star safety for the Army Black Knights football team, was drafted by the Detroit Lions in the seventh round of this weekend’s NFL draft. In doing so, he qualifies for the Army’s alternate service policy and is able to defer his active service commitment.

According to the policy, West Point graduates who sign a professional contract that “provides recruiting/public affairs benefits” may choose to postpone active service. They must spend two years as a recruiter and then either return to active service or refund a portion of their educational expenses and agree to six years in the Selected Reserve.

Instituted in 2005, the policy has been applied to just four cadets—all athletes. Campbell is the first football player and by far the most high profile.

Campbell is the latest in a long line of accomplished athletes from military academies. Most, however, never play professional sports. The most notable exception is 1963 Heisman Trophy winner Roger Staubach, who served in Vietnam before starting his Hall of Fame NFL career.

In the 1980s, Navy briefly allowed Napoleon McCallum to play in the NFL while serving. After just one season, the Navy ruled that the demands of the NFL were preventing McCallum from fulfilling his duties, and rescinded his right to play.

Campbell was drafted in the seventh and final round of the Draft and was the 218th overall pick. Fans at the NFL draft chanted, “Cal-eb Camp-bell” and “U-S-A, U-S-A” as Campbell was interviewed by ESPN analysts. Lions president Matt Millen called him a “smart and athletic guy. He can run, he's a great tackler, he's tough. Caleb certainly has a chance.”

ESPN’s E60 ran a documentary piece a week before the Draft that profiled Campbell and the Army’s policy. “It’s my duty to play NFL football,” Campbell said, “That’s my obligation. And being a recruiter, that’ll help the Army.” E60 also reported on Schuyler Williamson, a baseball player who used the exception to play minor league baseball. After a year, he decided he “needed to be somewhere else” and returned to active service, serving two years in Iraq.

During his sophomore season, Campbell considered transferring to another school to focus more on football. Army coach Bobby Ross convinced Campbell to stay, “using the exemption policy as a selling point.”

The Army instituted the policy in 2005 to boost recruiting, which was slipping during the wars in Iraq and Afghanistan. The first cadet to take advantage of the policy was Josh Holden, a baseball player who joined the Cincinnati Reds organization after graduation. He explained how he is serving his country by playing baseball and recruiting: “This is going to be a great thing for the Army. Eventually, this will bring better candidates to West Point … for professional sports or not.”

Because of the five-year service obligations, it is rare for a service academy athlete to play professional sports. Of the five Heisman trophy winners from academies, only Roger Staubach played more than a year in the NFL. He supports the current Army policy, saying, “I think it's good for the service academies if you have athletes that can compete at a higher level—and can still give back to the service—that they can find a compromise that allows them to play professional athletics. It's worth the effort to look at it and try to figure it out.”

In 1986, two athletes at Navy, football player Napoleon McCallum and basketball player David Robinson, had the potential to play professional sports. The Naval Academy relaxed its commitment rules so that McCallum could serve while also playing for the Oakland Raiders. In April 1987, the Navy repealed the “special accommodation” for athletes and McCallum was forced to fulfill his five-year service commitment. Meanwhile, Robinson, the first overall pick in the 1987 NBA draft, had grown too tall to be deployed. He served two years in the reserves and was the focus of Naval recruiting efforts; in 1989, he was allowed to begin his Hall of Fame NBA career.